The present invention relates to a disc brake for a vehicle, and more particularly, it relates to a disc brake of a caliper-floating type.
In general, a disc brake of a caliper-floating type comprises a pair of brake pads disposed on both sides of a disc rotor, and a carrier extending in a straddling relation to the outer periphery of the disc rotor. The carrier has a bridge portion for supporting the pair of brake pads to allow shifting movement in the axial direction of the disc rotor, and is secured to a non-rotating part of a vehicle disposed inwardly of the disc rotor in the vehicle. The disk brake also comprises a caliper body in which an operation portion containing a push mechanism for pushing an inner side pad (of the pair of brake pads) is disposed inwardly of the disc rotor, and in which a pawl portion for pushing an outer side pad (of the pair of brake pads) is disposed outwardly of the disc rotor in the vehicle. The pawl portion is interconnected to the operation portion and straddles the outer periphery of the disc rotor. Finally, a pin slide mechanism for supporting the caliper body is provided for shifting movement in the axial direction of the disc rotor with respect to the carrier.
Generally, in the conventional pin slide mechanism, a proximal (base) end of a pin is secured to each of left and right arm portions extending from both sides of the operation portion of the caliper body, and the pin is slidably inserted into a pin hole formed in the bridge portion of the carrier so that the caliper body is supported by the carrier in a cantilever fashion. However, in such an arrangement, a weight of the operation portion of the caliper body containing the pushing mechanism for pushing the inner side pad is considerably great. Therefore, a gravity center of the caliper is offset toward the interior of the vehicle. Due to such unbalance of weight, there arose problems that the caliper body is inclined with respect to the braking faces of the disc rotor during braking so as to cause an increase in drag torque and deterioration of the judder property, as well as an increase in vibration due to pin clearance. Further, due to such unbalance of weight, it is difficult to control a posture of the caliper body in assembling the caliper body on the carrier, thereby worsening an assembling ability. Particularly, in recent years, so-called electrically-driven disc brake (for an example, refer to International Publication WO 96/03301) in which an electrically-driven device is used as the pushing mechanism of the operation portion of the caliper body has been used relatively widely. In such a disc brake, however, since a weight of the operation portion of the caliper body housing the electrically-driven device is considerably increased, the above-mentioned problems become more noticeable. If they try to solve these problems, the pin slide mechanism must be made in a large size, which results in bulkiness of the disc brake.